Composite plated alloy material



United States Patent G 2,995,808 'COMPQSITE PLATED ALLOY MATERIAL Ernst Weisse, Klingerplatz 6, Hannover, Germany No Drawing. Filed Mar. 1, 1957, Ser. No. 643,240 Claims priority, application Germany Mar. '3, 1956 9 Claims. (Cl. 29-195) This invention relates to composite plated alloy material for manufacture of ornamental fittings and other parts, and more particularly to light-metal alloy material having a base of aluminum. By the term aluminum, I mean commercial pure aluminum (not less than 99% aluminum) or high purity aluminum (not leSs than 99.99% aluminum).

it is known that malleable alloys of the aluminumrnagnesium type, containing from 2 to magnesium, the rest being aluminum, normalized according to the current practice, cannot be directly plated to form composite metal plates by hot-rolling with aluminum or with other aluminum alloys, even if the cleaned core of the composite metal plates is kept clean and worked under protection of an inert gas or with air excluded from the parts being rolled. Up to now, all attempts to plate these aluminum-magnesium alloys directly with aluminum or with a layer consisting of aluminum and magnesium, have been unsuccessful.

The main object of the present invention is to achieve that result.

Another object is to provide an improved composition of aluminum-magnesium alloy suitable for plating upon a core or backing consisting of a malleable alloy of the aluminum-magnesium type.

Other objects and advantages of my invention will hereinafter appear from the following description.

The invention is based upon the realization that when the above-mentioned aluminum-magnesium alloys are heated, there is formed on the surface a thin harmful layer of magnesium nitrides and magnesium oxides, which layer makes the Welding of the plating layer to the core or backing impossible, and therefore success depends upon preventing the formation of this harmful layer. 1 have solved this problem by adding up to 0.5 beryllium to any aluminum-magnesium alloy containing more than 2% magnesium, which is to be used for making a composite light-metal alloy material. The amount of beryllium to be added to the aluminum-magnesium alloy must be chosen according to the percentage of magnesium in the alloy. For example, it is sufiicient to add 0.001% .beryllium to a malleable aluminum-magnesium alloy containing 3.5% magnesium, While a malleable alloy of aluminum-magnesium containing 7% magnesium must have about 0.05% beryllium added in order to exclude the formation of a layer of magnesium oxides and magnesium nitrides, which layer would prevent plating with an alloy.

Malleable alloys of the aluminum-magnesium type containing more than 2% magnesium and having added the necessary amount of beryllium, thereby excluding the formation of the above-mentioned harmful layer, which would prevent plating, are easily worked by hot-rolling in the known manner to produce a composite or multi-layer material, either with aluminum or with magnesium-containing alloys having a base of aluminum.

The present invention enables me to produce a composite or multi-layer light-metal material, the core or backing of which is covered with a hot-rolled plating of aluminum or of a malleable aluminum alloy, in which the core or backing of this composite material consists of a malleable alloy of the aluminum-magnesium type containing from 2 to 10% magnesium, with the addition of beryllium up to 0.5%, such addition rendering it possible to plate the core with said aluminum or malleable aluminum alloy.

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If the plating layer consists of aluminum alloy containing up to 10% magnesium, there is addedup to 0.5% beryllium, which renders it suitable for plating upon a core or backing of magnesium alloy containing from 2% to 10% magnesium with the addition of beryllium up to 0.5

If the magnesium percentage in the aluminummagnesium alloy of the plating layer is less than 2%, no addition of beryllium is necessary for plating, as the layer of oxides and nitrides forming when heated is so thin that it does not affect the plating operation. Consequently a layer of aluminum or of an aluminum alloy containing at most 2% magnesium, is suitable as plating without any addition of beryllium.

The composite or multi-layer plated material according to my invention can be used for manufacturing ornamental or other fittings, grills, bars and the like, particularly such as must have high tensile strength. If they are to be loaded or stressed, it is only necessary to form them in annealed or semi-hard state. They will possess, when formed, a tensile strength of 38 kg./mm. These ornamental fittings will therefore need no separate annealing or tempering, as necessary for the ordinary and easily plated high-tensile alloys of the aluminum-magnesiumsilicon, aluminum-copper-magnesium and aluminum-magnesium-zinc types; those alloys however need a special annealing and quenching treatment to obtain the desired high-tensile strength, and therefore require special furnace and a special working process for such heat treatment.

Example A specially important composite or multi-layer material according to the invention comprises a core consisting of a high-tensile malleable alloy of the aluminum-magnesium type containing up to 0.5 beryllium, and a plating made of aluminum or of an alloy containing a low percentage of magnesium with a base of aluminum. The outer layer of aluminum or magnesium-containing aluminum alloy, both based on aluminum 99.99% can be given a brilliant polish, either chemically or electrochemically by known methods. But this brilliant outer layer is relatively soft; it is therefore treated by an eloxal process as a protection against dents or scratches. The transparent film provided by the eloxal process only slightly reduces the sheen or polish, but it results in a glasshard and wear-resistant surface. Articles made of this composite or multi-layer material and treated in this manner will have an extremely high tensile strength and will give most satisfactory results during use.

Nearly all ornamental metalwork, grills and the like, is made by drawing; during such operation, the outer layer of a composite or multi-layer material will be highly stressed and there is therefore great danger of the surface being scratched or grooved in the draw, these markings having to be removed by grinding and polishing before the parts are given a highly polished appearance by known methods. To prevent grinding right through the outer layer of the part made from composite plated material according to the present invention, the outer layer should be made at least 0.2 mm. thick. Where fittings or other parts made of such composite or multi-layer lightmetal material are less stressed or not drawn, the outer layer may be of less thickness.

As examples of such high-tensile fittings made of my composite or multi-layer material, there may be mentioned automobile bumpers and over-riders therefor and vehicle Wheel hub-caps. These parts are usually made of sheet steel having a tensile strength of 35-38 kg./mm. being finally chromium-plated. Similar parts made from high-tensile light-metal alloy, consisting for example of aluminum with 5% magnesium, are not satisfactory in 3 use, because although they and scratches, even in the course of ordinary washing and cleaning. It is not possible to improve this particular material by an eloXal treatment, because the eloxal layer turns dull and opaque; neither can the parts be made of aluminum nor of an aluminum alloy containing a low percentage of magnesium, since this material is not strong enough. To secure equal strength, the parts made from these relatively soft materials would have to be about five times as thick as the same parts made of steel. On the other hand, the parts cannot be made economically of the aluminum alloys easily plated with aluminum, and strengthened by an annealing process, as such annealing of the parts would make large-scale manufacture diflicult and too expensive, apart from the fact that the parts would have to be subsequently rectified to remedy the distortion due to quenching them during such treatment.

In this respect, the composite or multi-layer material of my invention, made of high-tensile light-metal alloy of the aluminum-magnesium type, with an addition of beryllium as core, and a plating of aluminum (99.99%) or of a magnesium-containing alloy having a base of alumi num (99.99%), afiords a considerable technical and economical advance, because articles made of this material are far superior to chromium-plated steel parts. These light-metal parts having equal static strength can take up take a high polish, the com Paratively soft surface tends to become spoiled by dents "2,995,808 i in to 50% higher dynamic stress than the corresponding steel parts without becoming permanently deformed. Moreover, the gloss of these light-metal parts, made of material according to the invention and polished chemically or electro-chemically, is absolutely equal to the gloss of the chromium-plated steel parts. The eloxal treatment lends to the light-metal surface, on account of its extreme hardness, a considerably better resistance to scratching and denting than a chromium-plated surface can do for the steel parts, and the light-metal parts are much more resistant to corrosion than steel parts.

It is known from experience that chromium-plated steel parts will corrode in two years time at the most, in the atmosphere of a large industrial town. This drawback does not occur with light-metal parts made according to my invention, since neither the plating layer made of aluminum or of a magnesium-containing alloy having a base of aluminum, nor the core of malleable alloy of the aluminum-magnesium type, which is uncovered on the cut-edge of the parts, is susceptible of corrosion in the atmosphere of an industrial town, and the light-metal parts made of material according to my invention will keep their good appearance for many years.

What I claim is:

1. A composite plated sheet metal having a core and a plating intimately joined thereto by hot rolling wherein said core consists essentially of a corrosion resistant aluminum base alloy consisting essentially of from 2 to 10% magnesium and 0.0005 to 0.5% beryllium, the balance being aluminum, and whereinsaid plating consists essentially' of aluminum;

2. A composite plated sheet metal as defined in claim 1, wherein said plating includes up to 10% of magnesium and up to 0.5% of beryllium.

3. A composite plated sheet metal as defined in claim 1, wherein said core consists essentially of about 3.5% magnesium and 0.001% beryllium, the balance being aluminum.

4. A composite plated sheet metal as defined in claim 1, wherein said plating consists essentially of up to 2% magnesium, the balance being aluminum.

5. A composite plated sheet metal as defined in claim 1, wherein said core consists essentially of 7% magnesium and 0.05% beryllium, the balance being aluminum.

6. An ornamental metalwork formed from a composite plated sheet metal as defined in claim 1, the plating of said metal being finished by grinding, chemical polishing and anodizing.

7. A composite plated sheet metal as defined in claim 1, wherein said plating has portions having a thickness of at least 0.2 millimeter and wherein said metal has been finished by grinding, chemical polishing and anodizing.

8. An ornamental metalwork formed from a cold drawn composite plated sheet metal having a core and a plating joined thereto by' hot rolling wherein said core consists essentially of 2 to 10% magnesium and 0.0005 to 0.5% beryllium, the balance being aluminum, and wherein said plating consists essentially of aluminum.

9. An ornamental metalwork formed from a cold drawn composite plated sheet metal having a core and a plating joined thereto by hot rolling wherein said core consists essentially of 2 to 10% magnesium and 0.0005 to 0.5% beryllium, the balance being aluminum, and wherein said plating consists essentially of aluminum, said plating having portions having a thickness of at least 0.2 millimeter and having been finished by grinding, chemical polishing and anodizing.

References Cited in the tile of this patent UNITED STATES PATENTS 1,997,166 Brown Apr. 9, 1935 2,100,411 Reuleaux Nov. 30, 1937 2,273,483 Fink Feb. 17, 1942 2,336,512 Stroup Dec. 14, 1943 2,733,991 Willmore Feb. 7, 1956 2,821,014 Miller Jan. 28, 1958, 

1. A COMPOSITE PLATED SHEET METAL HAVING A CORE AND A PLATING INTIMATELY JOINED THERETO BY HOT ROLLING WHEREIN SAID CORE CONSISTS ESSENTIALLY OF A CORROSION RESISTANT ALUMINUM BASE ALLOY CONSISTING ESSENTIALLY OF FROM 2 TO 10% MAGNESIUM AND 0.0005 TO 0.5% BERYLLIUM, THE BALANCE BEING ALUMINUM, AND WHEREIN SAID PLATING CONSISTS ESSENTIALLY OF ALUMINUM. 